What do eluvial layers primarily lose?

Eluvial layers primarily lose minerals due to the process of leaching. In soil profiles, eluvial layers are found above the illuvial layers and are characterized by the downward movement of water, which carries away dissolved nutrients and minerals from the upper horizons during rainfall or irrigation. This leaching process results in reduced mineral content in the eluvial layers, making them less fertile compared to their counterparts.

In contrast, the other options do not accurately define what is primarily lost in the eluvial layers. While there may be some loss of water and organic matter in specific conditions, the defining characteristic of eluvial layers is their mineral depletion. Soil structure may also be modified by factors like moisture and compaction, but it is not the primary loss associated with eluvial layers. Thus, the emphasis on mineral loss clearly identifies the correct answer.